Study explores regional solar geoengineering to moderate El Niño impacts

A study published in Science Advances proposes using marine cloud brightening (MCB) to reduce the intensity of El Niño events by reflecting more sunlight over the Pacific Ocean. MCB involves spraying seawater into marine clouds to increase their reflectivity, a technique that has been tested in small-scale pilot projects and randomized controlled trials.

The authors, including climate scientist Katherine Ricke of UC San Diego and the Scripps Institution of Oceanography, used the 2019–2020 Australian bushfires as a natural analog. The fires emitted nearly 1 million metric tons of smoke into the stratosphere, which previous research links to the onset of a rare triple-dip La Niña—an opposite phase to El Niño—partly due to the reflective particles in the smoke.

The researchers modeled MCB’s effects by simulating reduced sunlight over the Pacific during two historic El Niño events. Their findings suggest that dimming sunlight in targeted regions could significantly reduce the magnitude of El Niño events and their global impacts, such as droughts, floods, and economic losses.

The study frames geoengineering not as a global temperature fix but as a regional intervention to relieve pressure points in the climate system. This approach contrasts with other solar geoengineering methods, such as stratospheric aerosol injection, which operate globally and carry broader uncertainties.

While the modeling indicates scientific feasibility, experts warn of substantial risks. Andrew Dessler, a professor of atmospheric science at Texas A&M University, described the idea as scientifically reasonable but emphasized that execution would be a "political nightmare," with potential for unintended consequences worse than the problems it aims to solve.

Katherine Ricke, the study’s coauthor, acknowledged the need for further modeling and caution before any real-world application. She noted that research into solar geoengineering is driven by the possibility of a future where fossil fuel pollution remains unchecked and climate impacts become unmanageable.